In this week’s Torah reading, Moshe reviews a series of laws governing the eventual appointment of a Jewish king. Moshe is aware that the Jewish people will want a king to rule over them, just as all the other nations have.
Although appointing a Jewish king is eventually permitted, there are special conditions that apply to Jewish kings. Jewish kings must be chosen by G-d. They must be from among the Jewish people and not foreigners. Jewish kings are forbidden from having too many horses and they also may not amass too much silver and gold for themselves.
Of particular interest is the ruling that any future Jewish king “must [also] not have too many wives, so that they not make his heart go astray.” How many is too many? According to the Talmud, an Israelite king was forbidden from having more than eighteen wives.
Polygamy was an accepted part of early Judaism. Avraham had both Sarah and Hagar as wives. Yaacov (Jacob) had four wives – the famous sisters Rachel and Leah and also two other, lesser-known wives – Bilhah and Zilpah. However, while polygamy was an accepted part of Biblical and early Jewish society, it is clear that is was never considered an ideal. Rabbi Joseph Telushkin notes that, if God had wished to communicate polygamy as an ideal, He would have created "Adam, Eve and Joan."
Although polygamy exists in the Bible, in every case, it leads to anguish. For example, when Hagar becomes pregnant before Sarah, there developed great animosity between Avraham’s wives. The Torah quotes Sarah saying about Hagar, “Now that she sees herself pregnant, she looks at me with disrespect.” About Hagar, the Torah says, “When she realized that she was pregnant, she looked at her mistress (i.e. Sarah) with contempt.”
Leah feels unloved and unhappy in her husband’s home (“God saw that Leah was unloved.”) and her sons come to hate Yosaif (Joseph) who is the son of the beloved Rachel (“Because of his dreams and words, they hated him even more.”).
Polygamy was an atavistic practice, left over from a less sophisticated time. The Torah did not immediately forbid it, but it is clear, as Judaism developed, especially as the prophets encouraged the people toward higher levels of moral and ethical behavior, that the incidence of polygamy decreased. Even when polygamy was permitted, monogamy was always considered the ideal form of partnership between a man and a woman.
Additional evidence that monogamy has always been preferred in Judaism is in the text of Aishet Chayil (“A Woman of Valor”). In these verses, customarily sung on Friday night, the woman of valor is clearly the only wife in the home. The prophets also compare the love between a husband and a wife to the love between G-d and the Jewish people. The implication is that, just as the Jewish people have no other G-d, the husband should have no other wife.
Although polygamy was legal in Jewish society for a long time, it was still quite rare, especially in the post-Biblical period. As evidence, over the hundreds of years that the Talmud was written, none of the rabbis of the Talmud had more than one wife.
Eventually, in the 10th century CE, the great Sage Rabbenu Gershom issued a rabbinic degree banning polygamy. Interestingly, polygamy has been illegal in Israel since the founding of the modern State in 1948.
Besides noting the unhappy outcomes in all Biblical stories of polygamy, Rabbenu Gershom also taught that polygamy constituted a chilul Hashem. A chilul Hashem is a behavior that makes Jews look bad in the eyes of others, especially among non-Jews. The concept of a chilul Hashem applies even today when the actions of one Jewish person reflect poorly on the community as a whole.
The opposite idea also exists. A Jewish person who behaves honorably is considered to have created a kiddush Hashem, a sanctification of G-d’s name in the larger world.
Thus, in a time when ordinary men could marry multiple wives, the ruling that a Jewish king must limit the number of his wives was revolutionary. Restricting the king to eighteen wives can be seen as part of the same progressive thinking that led to Rabbenu Gershom’s degree, which effectively ended polygamy in nearly every Jewish community even until today.